1. Field of the Invention
The present invention relates to carousel changers, and more specifically, to a carousel changer including a turntable having a plurality of trays to carry a plurality of disks thereon.
2. Description of the Related Art
A carousel changer is provided in a CD player, a DVD player or the like that serves as an optical disk changer. As shown in FIG. 5, a carousel changer 30 includes a turntable 20. The turntable 20 has a plurality of trays 1 around its rotating shaft 11. The trays each carry an optical disk such as a CD and a DVD thereon. The turntable 20 rotates counter-clockwise in FIG. 5 and transports a tray having an optical disk desired to be reproduced onto a reproducing device 13. An annular rack rail 8 is provided under the turntable 20. The rack rail 8 is engaged with a pinion gear 7 attached to a motor 12, and the turntable 20 is driven by the motor 12 to rotate. The carousel changer 30 further includes an annular rib R10 and a sensor 9 provided under the turntable 20. The rib R10 and the sensor 9 are used to place the center of a tray 1 carrying thereon an optical disk (that the user desires to reproduce) in the center of a support unit 14 in the reproducing device 13.
FIG. 6 is a sectional view taken along line VI-VI in FIG. 5. The rib R10 includes a plurality of recessed portions A1 and a plurality of raised portions B1. The recessed portions A1 and the raised portions B1 are used to identify the tray numbers of the trays 1, and place the center of a tray 1 in the center of the support unit 14. The sensor 9 has the rib R10 passed therethrough (though not in contact), detects recessed portions A1 and raised portions B1 of the rib R10 and outputs the result of detection to a controller 40. The controller 40 determines the tray number and stopping position of each of the trays 1 based on the detection result output from the sensor 9 and controls the motor 12 accordingly.
FIG. 7 is a partly developed view of the annular rib R10 shown in FIG. 6. The rib R10 has a stop area SA for stopping each tray 1 so that the center of the tray 1 is placed in the center of the support unit 14 and a count area CA for specifying the tray number of each tray 1. The turntable 20 in FIG. 5 includes six trays 1, and therefore the rib R10 includes six stop areas SA and six count areas CA. The stop area SA is made of a recessed portion ASA indicating a stopping position and two raised areas BSA having the recessed portion ASA therebetween. When the recessed portion ASA is subjected to the sensor 9, the center of a tray 1 is placed in the center of the support unit 14. The count area CA is made of a plurality of recessed portions ACA and a plurality of raised portions BCA. In FIG. 7, the plurality of raised portions BCA represent a tray number. When for example there are four such raised portions BCA, the count area CA indicates tray number “4.”
Referring to FIG. 8, it will be described how the carousel changer 30 operates to exchange an optical disk on a tray of number 3 (hereinafter as “tray No. 3”) with an optical disk on a tray of number 4 (hereinafter as “tray No. 4”).
When there is an optical disk on the tray with tray No. 3 on the support unit 14, the sensor 9 detects the recessed portion ASA3 in the stop area SA3 in the rib R10. Herein, the stop area SA3 refers to a stop area for the tray No. 3. The turntable 20 is stopped as the sensor 9 is subjected to (detects) the recessed portion ASA3 in the stop area SA3, the center of the disk on the tray No. 3 is positioned on the support unit 14. At time t1, a command to reproduce the disk on the tray No. 4 is externally given. At the time, the controller 40 supplies positive voltage V1 to the motor 12. In response to the applied positive voltage V1, the motor 12 drives the turntable 20 to start to rotate counter-clockwise. Immediately after time t1, the sensor 9 detects the raised portion BSA3 in the stop area SA3. At time t2, the sensor 9 detects the recessed portion ACA4 in the count area CA4 for the tray No. 4. At the time, the controller 40 determines that the raised portion BSA3 has passed the sensor 9 and the sensor 9 has started detecting the count area CA4. The controller 40 counts up the tray numbers by one each at time t3, t4, t5, and t6 when the sensor 9 detects a raised portion BCA4. In the count area CA4, the sensor 9 repeatedly detects the raised portion BCA4 and the recessed portion BCA4. If the sensor 9 cannot detect a raised portion BCA4 after starting detecting the recessed portion ACA4 for a prescribed period Δt, the controller 40 ends counting up of the tray numbers, and identifies the tray number. In FIG. 8, at time t8 the prescribed period Δt after time t7, the controller 40 specifies the tray number as “4.”
At time t9, the sensor 9 detects a raised portion BSA4 in the stop area SA4. The stop area SA4 is a stop area for the tray No. 4, and therefore the controller 40 determines that the stop area for the tray No. 4 has been entered. At the time, the controller 40 lowers the voltage supplied to the motor 12 from the voltage V1 to V2 and lowers the rotating speed of the turntable 20 accordingly. At time t10 when the sensor 9 detects the recessed portion ASA4 in the stop area SA4, the controller 40 temporarily supplies negative voltage V3 to the motor 12 to apply the “brake” and then stops supplying voltage. This stops the turntable 20.
The conventional carousel changer 30 determines the count end time for the tray number whether the prescribed period Δt elapses after the sensor 9 starts detecting a recessed portion ACA in the count area CA. Therefore, when the rotating speed of the turntable 20 changes by friction or the like caused by the pinion gear 7 or the rack rail 8, the count end time could be mistakenly determined. Since the width of the recessed portion ACA must be secured for the prescribed period Δt, the width of the raised portions BCA used for counting the tray numbers cannot be increased. When the tray number is “6,” at least six raised portions BCA must be provided in the count area CA, and the recessed portion ACA having the width corresponding to the prescribed time Δt must be provided in the count area CA. As a result, the width of the raised portion BCA is limited. It is difficult to form a raised portion BCA having a small width, and the portion with the small width is not strong enough.
In order to secure a strong rib, a rib R1 having a stop area SA and a rib R2 having a count area CA as shown in FIG. 9 may be used to control the rotation of the turntable 20. In this case, the tray number is determined by counting the recessed portions ACA in the rib R2, so that the width of raised portions BCA does not have to be small. However, the use of the two ribs necessitates the use of two sensors, which pushes up the manufacturing cost.